Rechargeable battery packs may provide a power source for cordless power tools. The battery pack may have a battery with a design voltage and may provide power to operate a power tool. The battery itself may consist of a number of individual battery cells that may be combined within the battery pack to provide a desired voltage. A lithium-ion battery may have a design voltage such as 18, 15, 12, or 9 volts, by way of non-limiting example. It may be desired to prevent charging and/or discharging of the cells in a lithium-ion battery when the temperature of the cells is above or below threshold values. The battery pack may contain a temperature sensor, such as a thermistor, to allow the temperature of the cells to be monitored. It may be desired to have the battery pack monitor its temperature with the thermistor when the battery pack is on a shelf or in a tool and to allow the charger to directly use the thermistor to monitor the temperature of the battery pack during charging.
The battery pack may undergo multiple charging operations at various charge current levels. To implement the charging at various charge current levels, a signal can be used to indicate when charging at one charge current level should cease. It may be desired to utilize a terminal on the battery pack to signal charge current reduction and/or termination to the charger while also utilizing this terminal to allow temperature measurement by the charger during the charging operation.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.